1. Field of the Invention
This invention relates to an improved hydraulic motor, and more particularly to a gerotor hydraulic motor having balance grooves configured for controlling hydraulic forces acting on a set of gerotor gears, so as to minimize frictional losses and maximize torque delivered to a load.
2. Description of the Related Art
Gerotor hydraulic motors are well known in the art. They comprise an inner gear and an outer gear, the axes of which are offset by a fixed distance. The inner gear is disposed interiorly of the outer gear and has exteriorly facing teeth that mesh with interiorly facing teeth on the outer gear. The outer gear is sized to have a sliding fit within a cylindrical housing. The inner gear is keyed to a driven shaft and meshes with the outer gear. The inner gear has one less tooth than the outer gear. The shape of the gear teeth is such that each tooth of the inner gear is always in sliding contact with a tooth of the outer gear. The resulting geometry creates discrete, multiple chambers that change from minimum to maximum and back to minimum volume for each rotation of the shaft.
A typical gerotor motor is driven by hydraulic fluid, received into a kidney-shaped chamber known as an inlet kidney port and discharged from a kidney-shaped chamber, known as an outlet kidney port. The flow of fluid past the inlet kidney port and into the gears causes rotation of the gear set as the gear chambers transition from minimum to maximum volume. The fluid is discharged through the outlet kidney port as the gear chambers transition from maximum to minimum volume. The hydraulic pressure drop between the inlet and outlet kidney ports varies from time to time as a function of resistive shaft torque, friction and volumetric displacement of the gear set. Further information regarding the construction and operation of gerotor devices may be found in Pareja. U.S. Pat. No. 4,199,305.
Gerotors may be used in pump applications, as well as in motor applications. In fact, gerotor pumps have a proven record of reliability and performance and are employed much more commonly than gerotor motors. One reason for this is the tendency of a gerotor motor to stall at initial start-up, even when no torsional load is applied to the motor shaft. Increasing the inlet pressure may help initiate rotation, but sometimes this only causes further binding of the shaft. Usually, a motor that begins to turn will continue to do so until the next time it comes to a complete stop.
Those skilled in the art will recognize this phenomenon as xe2x80x9chydraulic lock-upxe2x80x9d, characterized by an unbalanced hydraulic force acting on one or both gerotor gears, resulting in high static friction. The frictional forces often increase as pressure increases, sometimes consuming all of the torque generated by the motor. If the motor does begin to rotate, the friction from the hydraulic imbalance reduces the motor""s torsional efficiency and generates undesirable heat. This problem occurs in gerotor pumps, as well as gerotor motors. In that regard reference may be made to Pareja mentioned earlier herein.
FIG. 1 shows a typical radial pressure gradient in a prior art hydraulic gerotor motor. It may be observed that the inlet and outlet pressures act on the inner gear and cause a side load on the shaft. This load is supported by the shaft bearings. Torsional friction is minimal because of the small moment arm from the shaft axis to the shaft bearings. The inlet and outlet pressures also act on the outer gear and cause a similar side load against the housing gerotor bore. This can create significantly more torsional friction due to the larger moment arm. Note that there may be a starter-groove that ports fluid between the inside and outside of the outer gear. The purpose of this groove is to help balance the net radial pressure forces acting on the outer gear. Gerotor motor and pump manufacturers often use one or more starter-grooves. While these grooves offer limited improvement, experience has shown they do not provide consistent hydraulic balance required for a motor that starts reliably.
FIG. 1 shows why starter grooves are unreliable. Note that the radial pressure gradient varies from inlet pressure on the right side of the drawing (at the starter groove) to xe2x80x9csomexe2x80x9d low pressure on the left side of the drawing. The exact magnitude of the pressure is not defined except at the starter groove. Thus, for about 350 degrees of rotation, the pressure on the outside of the outer gerotor depends on radial and axial clearances, temperature and surface finish. If we find the sum of the hydraulic forces acting radially on the outside of the outer gerotor and add this to the sum of the hydraulic forces acting radially on the inside of the outer gerotor, the result should be near zero. Tolerances cause variations in the outside pressure gradient and the result is some will be poor starters. This is unacceptable for automotive cooling applications that must start every day, every time, at all temperatures for every motor produced.
Hydraulic balance is well known to engineers who design hydraulic pumps or motors.
Pumps are hydraulically balanced to reduce internal wear on rubbing parts and to minimize heat generation. This improves torsional efficiency. Pumps are typically driven by an electric motor and rarely (if ever) have a no-start problem as long as the motor can overcome the initial pump torsional friction. Once a pump begins to spin, a lubrication film builds up and tends to reduce rubbing friction. Note as well that typically hydraulic pressure is not generated until the pump begins to spin.
Hydraulic motors are especially sensitive to stalling unless they are xe2x80x9chydraulically balancedxe2x80x9d. Note that the generated torque increases as pressure increases but the frictional torque also increases as pressure increases. If the frictional torque is equal to the generated torque, the motor will not spin. This is called xe2x80x9chydraulic lockxe2x80x9d and is eliminated by hydraulically balancing the rubbing parts. However, prior to this invention there has been no fully satisfactory method for balancing gerotor motors. Existing gerotor balancing schemes have likely been aimed at gerotor pumps, not gerotor motors.
For years, engineers who design gerotor pumps and motors have attempted to balance them with xe2x80x9cstarter groovesxe2x80x9d in the gerotor bore. A good example is found in starter grooves 44, 46 shown Pareja U.S. Pat. No. 4,199,305. These starter grooves represent the current xe2x80x9cstate-of-the-artxe2x80x9d in gerotor pump and motor design and are commonly used in all designs. Unfortunately, they do not reliably minimize torsional friction and motors using these grooves will often stall.
FIG. 2 illustrates a typical axial pressure gradient in a prior art hydraulic gerotor motor and shows another deficiency of the prior art. Torsional efficiency is improved when the axial pressure gradient is the same on both sides of the inner and outer gears. This is particularly true of the outer gear since its moment arm to the shaft axis is larger than that of the inner gear. Often overlooked is the effect of radial leakage between the housing and cover plate. This leakage can be due to either an O-ring groove or to a low-pressure cavity. The leakage distorts the pressure gradient acting on the outer gear resulting in an axial pressure imbalance. A large undercut can similarly distort the axial (and radial) pressure gradient and further reduce torsional efficiency.
Another deficiency of the prior art is extreme sensitivity to gerotor/bore dimensional tolerances. Small variations in axial or radial clearances can dramatically change the critical radial and axial pressure gradients. In addition, temperature and surface finish can also cause wide variations in a motor""s torsional efficiency and, ultimately, ability to initiate rotation.
The invention described herein addresses these deficiencies of the prior art and offers much improved motor starting capability. While this invention is primarily directed at gerotor motors, those skilled in the art will recognize the benefits of this invention for gerotor pumps as well. The balance grooves defined by this invention reduce friction and improve torsional efficiency.
An object of this invention is to provide a gerotor device having improved torsional efficiency. A more particular object is to improve the startup torsional efficiency of a gerotor-type hydraulic motor. These objects are accomplished through the use of balance grooves between the clamped sealing surfaces of a gerotor housing and cover plate. In the preferred embodiment there are three such balance grooves. They include an inlet balance groove, an outlet balance groove and an axial balance groove. These grooves are located such that they are in direct contact with fluid at the periphery of the outer gear. They serve to balance axial and radial hydraulic pressure forces acting on the outer gear. The resulting net pressure force is substantially independent of both inlet and outlet pressure. This minimizes friction between the outer gear, housing and cover plate at all operating pressures; thereby improving motor starting capability and operating torsional efficiency.
Prior art hydraulic gerotor motors not equipped with the balance grooves of this invention have axial and radial pressure forces acting on the outer gear largely dependent on clearances, leakage and operating pressure. Small motor-to-motor dimensional variations can cause significant variations in the ability of a motor to start. This invention reduces the sensitivity to these clearances as well as variations of temperature, pressure, surface finish, and assembly.
In one aspect this invention comprises a hydraulic gerotor motor comprising: a housing provided with a cylindrical gerotor bore, an outer gerotor gear mounted within the gerotor bore, the outer gerotor gear having a smooth, cylindrical outer perimeter facing the gerotor bore to define a region of radial clearance therebetween, and an inner perimeter equipped with inwardly extending teeth, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, an inlet port situated for receiving a flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth an outlet port situated for discharging used hydraulic fluid from the device and a pressure balancing passage extending between the region of radial clearance and the inlet port, the pressure balancing passage having an arc length greater than 10 degrees.
In another aspect this invention comprises a hydraulic gerotor motor comprising: a manifold provided with a cylindrical gerotor bore, an outer gerotor gear mounted centrally within the gerotor bore, the outer gerotor gear having a smooth, cylindrical outer perimeter facing the gerotor bore to define a region of radial clearance therebetween, and an inner perimeter equipped with inwardly extending teeth, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, an inlet port situated for receiving a flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid from the device, and a pressure balancing passage extending between the region of radial clearance and the outlet port, the pressure balancing passage having an arc length greater than 10 degrees.
In still another aspect this invention comprises a hydraulic gerotor motor comprising: a manifold provided with pocket having a cylindrical side wall defined by a blind cylindrical opening extending perpendicularly into a plane surface, a cover plate clamped against the plane surface to seal the pocket, a cylindrical shaft extending into the pocket coaxially with the cylindrical opening an outer gerotor gear mounted within the pocket, the outer gerotor gear having a smooth, cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance therebetween, an inner perimeter equipped with inwardly extending teeth and a planar mounting surface extending between the inner perimeter and the outer perimeter, the planar mounting surface being sealingly clamped against the cover plate an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, an inlet port situated for receiving a flow of pressurized hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid from the device, and a pressure balancing passage extending between the region of radial clearance and the inlet port, the pressure balancing passage having an arc length greater than 10 degrees.
In yet another aspect this invention comprises a gerotor apparatus comprising: a manifold having a substantially planar first face and a pocket having a cylindrical side wall extending into the first face, a rotatable shaft extending axially into the pocket, an inner gerotor gear secured to the shaft and situated entirely within the pocket, the inner gerotor gear having a substantially planar second face coplanar with the first face and a circular perimeter provided with outwardly facing teeth, a generally annular outer gear having a smooth cylindrically extending outer gear perimeter, and a substantially planar third face, the outer gear being positioned inside the pocket such that the third face is coplanar with the second face, the outer gear also having a generally circular interior opening which is configured to define a number of uniformly spaced teeth extending radially inward, the number of teeth on the outer gear being one greater than the number of teeth on the inner gear, the outer gear being further positioned such that the inner gear is fitted within the opening of the outer gear and the inwardly extending teeth are in engagement with the outwardly extending teeth, the outer gear being still further positioned so as to define a region of radial clearance, a cover plate sealed against the third face and the second face to define a region of radial clearance between the side wall and the smooth outer gear perimeter, an inlet port connected to receive a supply of pressurized hydraulic fluid for delivery to a working region between the inner gear teeth and the outer gear teeth, an outlet port connected for discharging used hydraulic fluid from the device, and a pressure balancing passage extending between the region of radial clearance and the inlet port, the pressure balancing passage having an arc length greater than 10 degrees.
In still another aspect this invention comprises a method of operating a hydraulic gerotor motor of a type comprising a housing provided with a cylindrical gerotor bore, an outer gerotor gear mounted within the gerotor bore, the outer gerotor gear having an inner perimeter equipped with inwardly extending teeth, an inner gerotor gear mounted rotatably within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the outwardly extending teeth being fewer in number than the inwardly extending teeth, so that each tooth of the inner gerotor gear is always in sliding contact with a tooth of the outer gerotor gear thereby forming discrete multiple chambers which continuously change in size from a minimum to a maximum and back to a minimum with each rotation of the inner gerotor gear and an output shaft connected to and driven by the inner gerotor gear, the method comprising the steps of: delivering a hydraulic fluid to the chambers at a pressure and in a direction which balances all of the hydraulic forces acting on the outer gerotor gear, thereby avoiding frictional losses due to contact between the outer gerotor gear and the housing, and removing the hydraulic fluid from the chambers as they change in size from a maximum to a minimum.
In yet anther aspect this invention comprises a hydraulic device comprising at least one passage connecting inlet pressure to a radial clearance area between an outer gerotor and outer gerotor bore defining an inlet pressure region at the radial clearance, the center of the inlet pressure region being located at a first predetermined number of degrees from a radial line perpendicular to a gerotor offset and having an arc length a second predetermined number of degrees.
In still another aspect this invention comprises a hydraulic gerotor motor comprising a housing with first planar surface, a pocket defined by a blind cylindrical opening extending perpendicularly into the first planar surface, the pocket having a cylindrical side wall terminated by second planar surface, the second planar surface parallel to first planar surface, a cover plate with planar surface clamped against the housing first planar surface to seal the pocket, an outer gerotor gear mounted within the pocket, the outer gerotor gear having a cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance there between, inner perimeter of the outer gerotor gear equipped with inwardly extending teeth, the outer gerotor gear having two planar parallel surfaces perpendicular to the cylindrical outer perimeter, the planar surfaces providing a close running fit between housing second planar surface and the cover plate planar surface an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the inner gear having one less tooth than outer gear, a output shaft connected to and driven by the inner gerotor gear, an inlet port situated for receiving flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid, and a pressure balancing passage extending between the region of radial clearance and the inlet port, the pressure balancing passage causing creation of an inlet pressure region at the region of radial clearance, the inlet pressure region being centered within 20 degrees of a radial line from axis of the outer gerotor gear and perpendicular to a line joining the inner gerotor gear center and the outer gerotor gear center, the inlet pressure region having an arc length greater than 30 degrees.
In still another aspect this invention comprises a hydraulic gerotor motor comprising: a housing with first planar surface, a pocket defined by a blind cylindrical opening extending perpendicularly into the first planar surface, the pocket having a cylindrical side wall terminated by second planar surface, the second planar surface parallel to first planar surface, a cover plate with planar surface clamped against the housing first planar surface to seal the pocket, an outer gerotor gear mounted within the pocket, the outer gerotor gear having a cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance there between. inner perimeter of the outer gerotor gear equipped with inwardly extending teeth, the outer gerotor gear having two planar parallel surfaces perpendicular to the cylindrical outer perimeter, the planar surfaces providing a close running fit between housing second planar surface and the cover plate planar surface, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the inner gear having one less tooth than outer gear, a output shaft connected to and driven by the inner gerotor gear, an inlet port situated for receiving flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid, and a pressure balancing passage extending between the region of radial clearance and the outlet port, the pressure balancing passage causing creation of an outlet pressure region at the region of radial clearance, the outlet pressure region being centered within 20 degrees of a radial line from axis of the outer gerotor gear and perpendicular to a line joining the inner gerotor gear center and the outer gerotor gear center, the outlet pressure region having an arc length greater than 90 degrees.
In yet another aspect this invention comprises a hydraulic gerotor motor comprising: a housing with first planar surface, a pocket defined by a blind cylindrical opening extending perpendicularly into the first planar surface, the pocket having a cylindrical side wall terminated by second planar surface, the second planar surface parallel to first planar surface, a cover plate with planar surface clamped against the housing first planar surface to seal the pocket, an outer gerotor gear mounted within the pocket, the outer gerotor gear having a cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance there between. inner perimeter of the outer gerotor gear equipped with inwardly extending teeth, the outer gerotor gear having two planar parallel surfaces perpendicular to the cylindrical outer perimeter, the planar surfaces providing a close running fit between housing second planar surface and the cover plate planar surface, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the inner gear having one less tooth than outer gear, a output shaft connected to and driven by the inner gerotor gear, an inlet port situated for receiving flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid, and a pressure balancing passage defining an axial balance groove, the axial balance groove extending from the region of radial clearance, extending between the cover plate and the housing at a radius outside the region of radial clearance and extending to a second contact with the region of radial clearance.
In still another aspect this invention comprises a hydraulic gerotor motor comprising: a housing with two planar and parallel surfaces, a cylindrical opening extending perpendicularly through both planar surfaces defining a cylindrical side wall, a first cover plate with planar surface clamped against the housing planar surface to define a pocket, a second cover plate with planar surface clamped against second of the housing planar surface to seal the pocket, an outer gerotor gear mounted within the pocket, the outer gerotor gear having a cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance there between, inner perimeter of the outer gerotor gear equipped with inwardly extending teeth, the outer gerotor gear having two planar parallel surfaces perpendicular to the cylindrical outer perimeter, the planar surfaces providing a close running fit between the first cover plate and second cover plate, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the inner gear having one less tooth than outer gear, a output shaft connected to and driven by the inner gerotor gear, an inlet port situated for receiving flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid, and a pressure balancing passage extending between the region of radial clearance and the inlet port, the pressure balancing passage causing creation of an inlet pressure region at the region of radial clearance, the inlet pressure region being centered within 20 degrees of a radial line from axis of the outer gerotor gear and perpendicular to a line joining the inner gerotor gear center and the outer gerotor gear center, the inlet pressure region having an arc length greater than 30 degrees.
In yet another aspect this invention comprises a hydraulic gerotor motor comprising: a housing with two planar and parallel surfaces, a cylindrical opening extending perpendicularly through both planar surfaces defining a cylindrical side wall, a first cover plate with planar surface clamped against the housing planar surface to define a pocket, a second cover plate with planar surface clamped against second of the housing planar surface to seal the pocket, an outer gerotor gear mounted within the pocket, the outer gerotor gear having a cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance there between, inner perimeter of the outer gerotor gear equipped with inwardly extending teeth, the outer gerotor gear having two planar parallel surfaces perpendicular to the cylindrical outer perimeter, the planar surfaces providing a close running fit between the first cover plate and second cover plate, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the inner gear having one less tooth than outer gear, a output shaft connected to and driven by the inner gerotor gear, an inlet port situated for receiving flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid, and a pressure balancing passage extending between the region of radial clearance and the outlet port, the pressure balancing passage causing creation of an outlet pressure region at the region of radial clearance, the outlet pressure region being centered within 20 degrees of a radial line from axis of the outer gerotor gear and perpendicular to a line joining the inner gerotor gear center and the outer gerotor gear center, the inlet pressure region having an arc length greater than 30 degrees.
In still another aspect this invention comprises a hydraulic gerotor motor comprising: a housing with two planar and parallel surfaces, a cylindrical opening extending perpendicularly through both planar surfaces defining a cylindrical side wall, a first cover plate with planar surface clamped against the housing planar surface to define a pocket, a second cover plate with planar surface clamped against second of the housing planar surface to seal the pocket, an outer gerotor gear mounted within the pocket, the outer gerotor gear having a cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance there between. inner perimeter of the outer gerotor gear equipped with inwardly extending teeth, the outer gerotor gear having two planar parallel surfaces perpendicular to the cylindrical outer perimeter, the planar surfaces providing a close running fit between the first cover plate and second cover plate, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the inner gear having one less tooth than outer gear, a output shaft connected to and driven by the inner gerotor gear, an inlet port situated for receiving flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid, and a pressure balancing passage defining an axial balance groove, the axial balance groove extending from the region of radial clearance, extending between the first cover plate and the housing at a radius outside the region of radial clearance and extending to a second contact with the region of radial clearance.
In yet another aspect this invention comprises a hydraulic gerotor pump comprising: a housing with first planar surface, a pocket defined by a blind cylindrical opening extending perpendicularly into the first planar surface, the pocket having a cylindrical side wall terminated by second planar surface, the second planar surface parallel to first planar surface, a cover plate with planar surface clamped against the housing first planar surface to seal the pocket, an outer gerotor gear mounted within the pocket, the outer gerotor gear having a cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance there between. inner perimeter of the outer gerotor gear equipped with inwardly extending teeth, the outer gerotor gear having two planar parallel surfaces perpendicular to the cylindrical outer perimeter, the planar surfaces providing a close running fit between housing second planar surface and the cover plate planar surface, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the inner gear having one less tooth than outer gear, an input shaft connected to and driving the inner gerotor gear, an inlet port situated for receiving flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid, and a pressure balancing passage extending between the region of radial clearance and the inlet port, the pressure balancing passage causing creation of an inlet pressure region at the region of radial clearance, the inlet pressure region being centered within 20 degrees of a radial line from axis of the outer gerotor gear and perpendicular to a line joining the inner gerotor gear center and the outer gerotor gear center, the inlet pressure region having an arc length greater than 90 degrees.
In still another aspect this invention comprises a hydraulic gerotor pump comprising: a housing with first planar surface, a pocket defined by a blind cylindrical opening extending perpendicularly into the first planar surface, the pocket having a cylindrical side wall terminated by second planar surface, the second planar surface parallel to first planar surface, a cover plate with planar surface clamped against the housing first planar surface to seal the pocket, an outer gerotor gear mounted within the pocket, the outer gerotor gear having a cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance there between. inner perimeter of the outer gerotor gear equipped with inwardly extending teeth, the outer gerotor gear having two planar parallel surfaces perpendicular to the cylindrical outer perimeter, the planar surfaces providing a close running fit between housing second planar surface and the cover plate planar surface, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the inner gear having one less tooth than outer gear, an input shaft connected to and driving the inner gerotor gear, an inlet port situated for receiving flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid, and a pressure balancing passage extending between the region of radial clearance and the outlet port, the pressure balancing passage causing creation of an outlet pressure region at the region of radial clearance, the outlet pressure region being centered within 20 degrees of a radial line from axis of the outer gerotor gear and perpendicular to a line joining the inner gerotor gear center and the outer gerotor gear center, the outlet pressure region having an arc length greater than 30 degrees.
In still another aspect this invention comprises a hydraulic gerotor pump comprising: a housing with first planar surface, a pocket defined by a blind cylindrical opening extending perpendicularly into the first planar surface, the pocket having a cylindrical side wall terminated by second planar surface, the second planar surface parallel to first planar surface, a cover plate with planar surface clamped against the housing first planar surface to seal the pocket, an outer gerotor gear mounted within the pocket, the outer gerotor gear having a cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance there between, inner perimeter of the outer gerotor gear equipped with inwardly extending teeth, the outer gerotor gear having two planar parallel surfaces perpendicular to the cylindrical outer perimeter, the planar surfaces providing a close running fit between housing second planar surface and the cover plate planar surface, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the inner gear having one less tooth than outer gear, an input shaft connected to and driving the inner gerotor gear, an inlet port situated for receiving flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid, and a pressure balancing passage defining an axial balance groove, the axial balance groove extending from the region of radial clearance, extending between the cover plate and the housing at a radius outside the region of radial clearance and extending to a second contact with the region of radial clearance.
In another aspect this invention comprises a hydraulic gerotor pump comprising: a housing with two planar and parallel surfaces, a cylindrical opening extending perpendicularly through both planar surfaces defining a cylindrical side wall, a first cover plate with planar surface clamped against the housing planar surface to define a pocket, a second cover plate with planar surface clamped against second of the housing planar surface to seal the pocket, an outer gerotor gear mounted within the pocket, the outer gerotor gear having a cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance there between. inner perimeter of the outer gerotor gear equipped with inwardly extending teeth, the outer gerotor gear having two planar parallel surfaces perpendicular to the cylindrical outer perimeter, the planar surfaces providing a close running fit between the first cover plate and second cover plate, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the inner gear having one less tooth than outer gear, an input shaft connected to and driving the inner gerotor gear, an inlet port situated for receiving flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid, and a pressure balancing passage extending between the region of radial clearance and the inlet port, the pressure balancing passage causing creation of an inlet pressure region at the region of radial clearance, the inlet pressure region being centered within 20 degrees of a radial line from axis of the outer gerotor gear and perpendicular to a line joining the inner gerotor gear center and the outer gerotor gear center, the inlet pressure region having an arc length greater than 90 degrees.
In yet another aspect this invention comprises a hydraulic gerotor pump comprising a housing with two planar and parallel surfaces, a cylindrical opening extending perpendicularly through both planar surfaces defining a cylindrical side wall, a first cover plate with planar surface clamped against the housing planar surface to define a pocket, a second cover plate with planar surface clamped against second of the housing planar surface to seal the pocket, an outer gerotor gear mounted within the pocket, the outer gerotor gear having a cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance there between. inner perimeter of the outer gerotor gear equipped with inwardly extending teeth, the outer gerotor gear having two planar parallel surfaces perpendicular to the cylindrical outer perimeter, the planar surfaces providing a close running fit between the first cover plate and second cover plate, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the inner gear having one less tooth than outer gear, an input shaft connected to and driving the inner gerotor gear, an inlet port situated for receiving flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid and a pressure balancing passage extending between the region of radial clearance and the outlet port, the pressure balancing passage causing creation of an outlet pressure region at the region of radial clearance, the outlet pressure region being centered within 20 degrees of a radial line from axis of the outer gerotor gear and perpendicular to a line joining the inner gerotor gear center and the outer gerotor gear center, the inlet pressure region having an arc length greater than 30 degrees.
In still another aspect this invention comprises a hydraulic gerotor pump comprising a housing with two planar and parallel surfaces, a cylindrical opening extending perpendicularly through both planar surfaces defining a cylindrical side wall, a first cover plate with planar surface clamped against the housing planar surface to define a pocket, a second cover plate with planar surface clamped against second of the housing planar surface to seal the pocket, an outer gerotor gear mounted within the pocket, the outer gerotor gear having a cylindrical outer perimeter facing the cylindrical side wall to define a region of radial clearance there between. inner perimeter. of the outer gerotor gear equipped with inwardly extending teeth, the outer gerotor gear having two planar parallel surfaces perpendicular to the cylindrical outer perimeter, the planar surfaces providing a close running fit between the first cover plate and second cover plate, an inner gerotor gear mounted within the outer gerotor gear, the inner gerotor gear having outwardly extending teeth engaging the inwardly extending teeth of the outer gerotor gear, the inner gear having one less tooth than outer gear, an input shaft connected to and driving the inner gerotor gear, an inlet port situated for receiving flow of hydraulic fluid and delivering the hydraulic fluid to a region of engagement between the inwardly extending teeth and the outwardly extending teeth, an outlet port situated for discharging used hydraulic fluid and a pressure balancing passage defining an axial balance groove, the axial balance groove extending from the region of radial clearance, extending between the first cover plate and the housing at a radius outside the region of radial clearance and extending to a second contact with the region of radial clearance.
The advantages offered by the invention will become apparent to those skilled in the art upon reading the attached detailed description of the preferred embodiment and with the aid of the accompanying drawings.